- A mild and efficient reaction for conversion of carboxylic acids into acid bromides with ethyl tribromoacetate/triphenylphosphine under acid-free conditions
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Acid bromides were prepared efficiently from carboxylic acids with readily available ethyl tribromoacetate and triphenylphosphine at room temperature under neutral conditions. The present process is applicable to the preparation of various acid bromides from aromatic and aliphatic carboxylic acids. Aromatic carboxylic acids were found to be more reactive than aliphatic carboxylic acids under reaction conditions.
- Kang, Dong Ho,Joo, Tae Young,Lee, Eun Hwa,Chaysripongkul, Skaydaw,Chavasiri, Warinthorn,Jang, Doo Ok
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p. 5693 - 5696
(2007/10/03)
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- Kinetic and Spectroscopic Studies on Acyl Radicals in Solution by Time-Resolved Infrared Spectroscopy
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A number of acyl radicals, R=O, have been generated in hexane or di-t-butyl peroxide as solvent at room temperature by 308 nm laser flash photolysis, and their spectroscopic and kinetic properties have been examined by time-resolved infrared spectroscopy.The C=O stretching frequencies for the R=O radicals are found to be higher than those of the corresponding aldehydes, RCHO, by between 108 and 128 cm-1, an effect attributed to a higher C=O bond order in the radicals.For the R=O radicals some typical values of νC=O are: CH3=O, 1864 cm-1; (CH3)3C=O, 1848 cm-1; and C6H5=O, 1828 cm-1, while the corresponding acylperoxyl radicals, RC(O)OO, formed by reaction with oxygen have νC=O values of 1838, 1840 and 1820 cm-1, respectively.The acyl radicals exhibit a reactivity towards a variety of substrates that is roughly comparable to that of simple alkyl radicals.For reactions of the benzoyl radical some typical rate constants/M-1s-1 are: CCl4, 6.0*104; C6H5SH, 4.8*107; CCl3Br, 2.2*108; Tempo, 1.1+109; and oxygen, 1.8*109.Alkanoyl radicals have a rather similar reactivity to benzoyl.The propanoyl radical reacts with tributyltin deuteride with a rate constant of 3*105 M-1s-1.The hex-5-enoyl radical undergoes a 5-exo-trig cyclization to form the 2-oxocyclopentylmethyl radical with a rate constant of 2.2*105 s-1, a value which is almost identical to that for cyclization of the hex-5-enyl radical.It is hoped that our kinetic data will prove useful in the planning of organic synthetic strategies which involve acyl radical chemistry.
- Brown, Carl E.,Neville, Anthony G.,Rayner, David M.,Ingold, Keith U.,Lusztyk, Janusz
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p. 363 - 380
(2007/10/02)
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- Noncompeting Metastable Losses of Methyl and Ethylene from Gaseous Butanoic Acid Ions due to Isomerization Prior to Methyl Loss
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Metastable C4H8O+. ions obtained from butanoic acid and ethyl butanoate undergo considerable γ-hydrogen exchange prior to losing ethylene, but little exchange prior to losing methyl.Therefore the two fragmentations are not directly competing, contrary to the general assumption that all reactions of an ion in the gas phase are competitive.It is concluded that metastable butanoic acid ions which lose methyl isomerize essentially irreversibly to CH3CH2C.HC(OH)2+ and/or CH3CH(C.H2)C(OH)2+ before the γ-methyl becomes exchanged.This accounts for the difference between γ-hydrogen exchange prior to the loss of methyl and ethylene without invoking isolated electronic states, as previously proposed.Butanoic acid ions generated by the McLafferty rearrangement of butanoate esters have a much weaker metastable loss of ethylene than directly ionized butanoic acid.Collisional activation experiments demonstrate that this results from more of the butanoic acid ions derived from ethyl butanoate than from butanoic acid isomerizing prior to collision.Variation in internal energy probably causes this difference in degree of isomerization with the source of the ion.
- McAdoo, David J.,Hudson, Charles E.
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p. 7710 - 7713
(2007/10/02)
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- 2-Acyl-3-substituted cyclopentan-1-ones and process for their preparation
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1,3-Dicarbonyl compounds useful as medicines, agricultural chemicals, perfumes, and their intermediates are prepared by reacting a specific α,β-unsaturated carbonyl compound with a specific organic copper lithium compound in the presence of an aprotic inert organic solvent, and then reacting the reaction product with an organic carboxylic acid halide or anhydride. In particular, novel 2-acyl-3-substituted cyclopentan-1-ones and 2-acyl-3-substituted cyclohexan-1-ones having important physiological activities are provided.
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